This might be related to issue 1166 (which also has a related long
conversion error that's marked against 2.5beta0).
To answer the questions posed there --- this is not a 64bit JVM (it's a
32bit Java 1.5 on Mac OS X, build 1.5.0_16-b06-284) and os._native_posix
is true.

Hmm. It's always reproducible here. However: I am running Jython embedded
inside my own application.
And (just checked), from inside the jython command line wrapper, "import
random" works just fine.
Yikes. The application is open source (http://openendedgroup.com/field) but
it's going to put everybody a long way from any bug inside Jython. I'll
start taking a closer look and report back.